The invention relates to a brake disk and method for producing a friction ring, particularly for brake disks having friction rings constructed of more than one ring part, particularly axle brake disks for rail vehicles having two axially offset ring bodies divided corresponding to the friction ring and a method for their manufacturing are known in a plurality of constructions.
Patent Document DE 43 08 910 C2 discloses a brake disk for disk brakes with a friction ring which can be acted upon on one side by at least one brake shoe and has at least two friction ring segments. Each ring segment is held on a carrier body by connection elements which prevent radial relative displacements of the ring segments. The friction ring also has recesses on at least one side which are open toward the carrier body and are symmetrically arranged with respect to the junction points of the ring segments. The recesses are shallower than the width of the ring segments.
Furthermore, the friction ring has ring grooves as recesses which are arranged bridging the junction points and whose axes extend parallel to the axis of the friction ring, in which case a ring body can be inserted in each ring groove and fills the ring groove at least approximately completely and bridges the junction point. This arrangement prevents the junction point between the two ring segments from growing wider in the event of an occurrence of high centrifugal or other forces. Relative radial displacements also avoided. The connection elements as constructed require-virtually no additional installation space.
However, this solution is very costly to make because the recesses and ring bodies must be precisely cut. Furthermore, in addition to the division, an additional high-expenditure machining of the ring segments is required. A casting is also conceivable, but requires a special casting mold.
European Patent Document EP 0 166 879 B1 shows a brake disk with a divided friction ring, particularly an axle brake disk for rail vehicles having two axially offset ring bodies divided corresponding to the friction ring. Two mutually axially opposite ring bodies are connected with one another by radially extending ribs. A screwed connection bridges the mold seam between the friction ring parts with prestress, the mutually opposite faces of the friction ring parts in the areas of the screwed connection and their lateral boundary resting against one another but have a distance from one another in the remaining areas. The screwed connection enables the ring bodies to experience a secure connection with no gaps in the friction surfaces of the brake disk. In addition, unintentional deformations of the ring bodies and the buildup of excess tensions is avoided. This solution is also costly to make.
European Patent Document EP 0 636 217 B1 shows a one-piece brake disk with two separation zones dividing it into two parts. Subsequently, a fastening device is positioned on each separating zone and extends over this separating zone. Finally the brake disk is broken at the separating zones into two semicircular parts. This method is relatively inexpensive because the brake disk itself can be manufactured at low cost, and the replacement of a worn-out brake disk with a new brake disk is quite simple. However, corresponding connection elements must be provided to prevent relative displacement of the ring segments. Another significant disadvantage is that this method can only be used for brake disks made from brittle materials, such as gray cast iron. Furthermore, these brittle friction rings must be thick and heavy in order to avoid fracture. As a result, such friction rings are not suitable for a use in rail vehicles because, as a rule, only wide friction rings are used there. However, these cannot be broken but at most can be destroyed. Another disadvantage is the resulting further development of the profile surface. However, the breakage zone does not prevent unevennesses in the surface of the friction ring. Therefore, deeper zones of wear may occur, which may result in an uneven wearing of the brake linings.
Furthermore, the solutions described in the indicated patent documents are not cost-effective for the manufacturing of brake disks of a small width and their design for higher speeds.
The present invention further develops a brake disk having a divided friction ring such that the disadvantages indicated in the prior art are avoided. Simple devices are used such that the junction point between two ring segments cannot widen even when high centrifugal forces or other forces occur, and simultaneously an axial and radial displacement relative to one another is avoided. The connection elements require virtually no additional installation space, so that the brake disk can also be constructed to be unventilated or with only short cooling ribs. Furthermore, this brake disk is inexpensive to make.
The brake disk comprises a friction ring having at least two ring segmentsxe2x80x94a first ring segment and a second ring segment. The ring segments are produced by a mechanical separation process from a one-piece or one-part ring-shaped basic body. According to the invention, the separation of the ring segments from the basic body is done by a hydrocutting method, particularly a water torch cutting method. The separating line is constructed such that the end areas engage in one another while forming a separation gap therebetween.
The area of contact between the segments is called a junction area or separation area. In this case, the term xe2x80x9cjunction areaxe2x80x9d relates to the meeting of the mutually opposite surfaces of the two mutually adjacent ring segments under stress, while these surfaces are to be assigned to the xe2x80x9cseparation areaxe2x80x9d under the aspect of the course of the separating line of the ring-shaped basic element in the circumferential direction. The adjacent ring segments are coupled with one another in the separation or junction area by means of at least one connection element. The at least one connection element extends along and passes through at least a partial area of the end areas of the ring segments. This reduces the space requirement for the installation of the connection elements. When the brake lining is in contact with the friction ring, the connection elements do not project beyond the latter and cannot damage the brake lining.
The meshing of the individual ring segments in the junction or separation area is accomplished by protrusions and recesses are formed on the respective mutually opposite separation surfaces of the individual friction ring segments. These protrusions and recesses are complementarily formed so that the protrusions of one segment engage in recesses on the other ring segment.
The method according to the invention has a minimal number of required process steps and a low requirement of installation space and at low cost. The basic element may already be finished with respect to its surface treatment because, after the cutting operation, no additional surface-processing steps are required for the surface machining. For this reason, conventional one-piece friction rings can also be used as the one-piece basic element.
The very fine hydrojet or water torch generates only a minimal cutting gap, resulting in a low loss of material, and the individual ring segments can therefore be fitted into one another with a very accurate fit. This separation gap caused by the cutting, is in the one millimeter range, which virtually ensures a contact of the end areas of the individual ring segments. When the ring segments are connected, no additional measures are generally required to fix the position of the individual elements with respect to one another. When the individual ring segments are mounted, the connection is capable of absorbing all circumferential tensions on the friction ring.
The technique of hydrocutting, particularly water torch cutting, is a type of mechanical separation which, in addition to its suitability for very complex shapes and undercuts, permits a machining with very little deformation in the area of the cut. As a result, no additional surface treatment of the separation surfaces is required after the cutting operation.
Few limits are set as far as the types of used materials that may be used.
Metals of various types, such aluminum alloys, nonferrous metals, or even glass, laminated glass, ceramics, and plastic materials as well as composite materials can be worked. The high environmental compatibility in comparison to other separation processes is particularly advantageous. This also does not result in additional tool costs and requires only very low mounting costs.
Another advantage of the inventive process is the fact that even thick friction rings can be cut with low tolerances, in which case the cutting operation takes place in an environmentally friendly manner and with very little thermal or mechanical deformation. Complex shapes, particularly with respect to the design of the recesses and protrusions, can therefore be easily produced. This separation process also does not set any limits to the arrangement of the separation points with respect to their mutual spacing, regularity, or symmetry.
In order to be able to manufacture also very thin friction rings consisting of at least two ring segments at reasonable cost, the junction or separation area is reinforced on the uncut basic element so that the connection elements can be enclosed within the junction or separation area. The area may be reinforced by an accumulation of additional material, or by making the junction and separation area thicker.
In this reinforced area, a passage opening, preferably in the form of a passage bore, is made in the radial direction. The passage bore is preferably made before the segments are cut. The friction ring can then be separated already in the finished condition by means of the water torch process.
During the hydrocutting, the energy required for the separation is applied by a liquid jet flowing through a very fine ceramic or precious-stone nozzle. There are numerous possibilities for the construction the water torch. Only a few examples will be discussed here. A relatively high pressure is required to create the fine water jet. Therefore, an oil admission pressure is generated in a primary circulation system usually using a high-pressure hydraulic pump. This oil admission pressure is converted into a high water pressure in a secondary circulation system. The high-pressure pump should generate a water pressure of up to approximately 3,800 bar, which flows through the water nozzle in the cutting head at a approximately 2.5 times the velocity of sound. A cutting agent of an extremely fine grain is supplied to the directed water jet in the mixing chamber, in order to create a microcutting. For this purpose, a vacuum assists in urging the abrasive agent from the storage container and into the chamber. After the removal of the abrasive agent from the storage container, this agent is supplied to a metering device. Here, the abrasive quantity may be selectively adjusted as required for the cutting task.
The abrasive jet will then be newly directed onto the workpiece. A fine-grained olivine sand or granite sand as well as corundum can be used as the abrasive. The harder the material of the friction ring, the better the removal performance. The abrasive unit essentially has the following components:
abrasive cutting head, abrasive metering system, controlled inlet/outlet valve and abrasive container for the permanent providing of several different cutting additions.
During the high-power abrasive operation, residual energy may be dissipated by an energy absorber integrated in the water tank.
The friction ring produced by the inventive process can be used in vehicles having disk brakes. The brake disk comprises at least one friction ring which can be acted upon on one side by at least one brake shoe and which consists of at least two ring segments each held on a carrier body. The end areas of the ring segments engage one another while maintaining a small gap therebetween. The segments are coupled with one another by means of connecting devices. The invention comprises the following possible ways of coupling the segments:
a) Coupling by means of one connection element respectively in the region of the separation or junction areas;
b) coupling by means of several connection elements respectively in the region of the separation or junction areas.
In the former case, the connection elements are arranged generally along radii of the brake disk, which therefore permits a hinged connection between the individual friction ring elements. In this case, the hinge axis is aligned such that it is situated essentially in a plane which extends perpendicularly to the diameter the brake shoe or of the friction ring. With respect to the implementation of the articulated connection, a large number of possibilities exist, in which case at least one hinge is provided. This hinge has a hinge axis which extends in the radial direction along at least a portion of the course or dimension of the friction ring in the radial direction. Relative to the axis of symmetry of friction ring, the hinge axis extends perpendicularly. In this case, the hinged connection permits at least one swivelling movement of the two friction ring segments which are coupled with one another. During relative movements of the individual friction ring segments against one another, particularly during the implementation of the swivelling movement corresponding to the hinged connection, as it may be desired particularly when a friction ring segment is removed, damage by frictional work is avoided.
The connection elements are arranged in the area of the meshing of the protrusions and recesses and extend through the protrusions of the first ring segment and of the second ring segment.
In either of the above-mentioned cases, connection elements are used in the form of connection pins, plug-type bolts, screws, or pins to displacement in the radial direction as a result of the centrifugal effect. These devices can be formed either directly by the connection element or by a separate element which can be coupled with the connection element.
There are numerous embodiments regarding the arrangement of the protrusions and recesses on the two respective mutually facing surfaces of the individual friction ring segments:
a) alternately at a constant distance;
b) alternately at a different distance or a different width of the individual protrusions and recesses, in which case care should be taken that complementary recess and protrusions are provided in each case on the complementary component.
The mutually facing surfaces of the mutually adjacent ring segments are also called junction surfaces or separation surfaces, the term xe2x80x9cjunction surfacexe2x80x9d essentially relating to the fact that the two surfaces come in contact with one another at least indirectly, while the term xe2x80x9cseparation pointxe2x80x9d relates to the producing of the ring segment according to the invention. In the case of the further development of the junction and separation surfaces, each has partial areas which are radially aligned and also areas which are perpendicular to the radial direction, or at an angle thereto.
Under another aspect of the invention, devices may be provided to reduce relative radial displacement of the ring segments with respect to one another of the gap which, although it is small, occurs during the separation operation according to the invention corresponding devices are provided. These may, for example, comprise
a) spacers in the separation gap and/or
b) adjusting screws and/or
c) plain washers at the end of the connection elements and/or
d) sliding guides between the ring segments and the elements forming the holding device for the ring segments.
The spacers are preferably arranged in the partial areas of the separation gap which extend or are aligned in the circumferential direction. Analogously, this applies to the use of adjusting screws which also act in the separation gap areas aligned in the circumferential direction.
Furthermore, the invention is suitable for the manufacturing of friction rings for brake disks for applications having high rotational speeds.
In another embodiment of the invention, a high bending strength of the friction ring is achieved by a multiple-shear connection of the individual friction ring segments with one another. Passage openings are provided in the separation area. Preferably, at least two openings are provided and are arranged parallel to one another and permit the accommodation of connection elements. In either the, the passage openings are radially aligned.
Under another embodiment of the invention, the separation gap is filled with a special element, for example, a sheet metal strip. The wheel brake disk will then resist bending in the separation area and, in the circumferential direction, will act similarly to an undivided friction ring. This special element can be made as one piece, or may be a multipiece construction. However, care should be taken that, in the areas of the separation gap, the sheet metal strip has an opening for receiving the connection elements. The individual special elements, particularly the sheet metal strips, extend at least along a partial area of the separation gap. An embodiment with a complete filling of the separation gap in the width direction is also conceivable. In this case, corresponding passage openings for the connection elements would have to be provided, while in the other case only recesses would have to be provided on the sheet metal strip.
According to the invention, a further development of a friction ring made of several ring segments is shown. These individual ring segments mesh with one another and are coupled with one another by way of at least one connection device.
As a result of this type of connection, the two friction ring segments are sufficiently secured in the axial as well as in the radial direction and, in addition, in the circumferential direction.
In the following, the invention will be explained by means of figures.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.